Liquid storage pit with floating cover

ABSTRACT

Means for storing liquids including a storage pit having an inclined wall and provided with a floating cover, said floating cover comprising a plurality of buoyant elements movably interconnected in a fluidtight manner.

United States Patent 1 1 3,592,009

[72] Inventors Teunis Glijnis [50] Field olSearch 6l/l,5,7; Alkmaar; 220/26 Petrus J. Antonissen, The Hague; Cornelis J. Kamp, The Hague, all of, Netherlands References it d [2] Appl. No. 820,165 UNITED STATES PATENTS 1 FM 1"- 1969 2.970716 2/1961 McCammon 61/.5 x 1 3,029,971 4/1962 Reynolds 1. 220/26 [731 Asslgm 3,079,030 2/1963 Moyer 220/26 New York, N.Y. 3,383,863 5/1968 Berry 61/7 X [321 Pmmy May P 3,445,026 5/1969 Korn 220/26 133] g g' 3,461,673 8/1969 Slover 61/7 x 1 335 3 3.462040 8/1969 Galloway 220/26 Primary Examiner-Peter M. Caun Attorneys-Thomas R. Lampe and J. H. McCarthy s4 LIQUID STORAGE PIT WITH FLOATING COVER 3 u Clams 9 Drawmg Flgs' ABSTRACT: Meansfor storing liquids including a storage pit [52] US. Cl 61/.5, having an inclined wall and provided with a floating cover,

220/26 said floating cover comprising a plurality of buoyant elements [5 l 1 Int. Cl 865g 5/00 movably interconnected in a fluidtight manner.

PAIENTED JUL 1 319m SHEET 1 0F 5 wmmaw INVENTORS:

TEUNIS GLIJNIS PETRUS J. ANTONISSEN PATENTED JUL 1 3 Ian SHEET 2 [1F 5 INVENTORS:

TEUNIS GLIJNIS PETRUS J. ANTONISSEN CORNELIS J. KAMP BY:

THEIR ATTORNEY PATENTEUJuuamn 3.592008 SHEEI 3 [IF 5 3 a (J s a B U 4 S s g QI g 4 4 FIG. 5

INVENTORS:

TEUNIS GLIJNIS PETRUS J. ANTONISSEN CORNELIS J. KAMP TEUNIS GLIJNIS PETRUS J. ANTONISSEN CORNELIS J. KAMP THEIR ATTORN Y PATENTEI] JUL] 31971 3,592 O09 SHEET 5 0r 5 FIG. 8

FIG. 9

INVENTORS:

TEUNIS GLIJNIS PETRUS J. ANTONISSEN CORNELIS J. KAMP aYz/d w THEIR ATTORNE LIQUID STORAGE PIT WITH FLOATING COVER The invention relates to means for storing liquids. said means comprising walls and provided with a floating cover SUMMARY OF THE INVENTION It is an object of the present invention to provide a pit of the above type. in particular but not only. suitable for storing crude oil, and which has the advantage that it is of relatively simple and inexpensive construction. It is known that a liquid such as crude oil has to be stored temporarily in large quantities, particularly nowadays and in the near future, since tankships are becoming larger and larger because of the growing consumption of crude oil. Consequently, it is desirable to develop a storage reservoir for crude oil in which new relatively cheap materials can be used, so that the cost per unit or storage volume will be as low as possible.

A simple and inexpensive reservoir for storing crude oil would be a pit made in the ground, partly in the ground and partly above the ground, or completely above the ground. In view of the volatile components present in crude oil it is, however, necessary to provide the pit with a roof or cover to prevent evaporation of the volatile components present in the crude oil.

Consequently, it is another object of the invention to provide a floating cover for a pit dug out in the ground and having inclined walls, said floating cover being of such a construction that it can be simply made of relatively cheap materials.

Therefore, the invention comprises a liquid storage pit having an inclined wall and provided with a floating cover, comprising a number of buoyant elements movably interconnected in a fluidtight manner by thin flexible fluidtight sheets, the buoyant elements at the periphery of the floating cover being anchored to the upper part of the inclined wall of the pit.

In carrying out the teachings of the present invention, the buoyant elements may consist at least partly of a foamed artificial resin or plastic, for example polyurethane foam.

It is another object of the invention to provide the walls of the pit with a lining of relatively cheap materials preventing the storage liquid, such as crude oil, from impregnating the ground around the pit. Thus, the bottom and sidewalls of the pit are lined with glass fiber reinforced epoxy resin, preferably mixed with coal tar.

DESCRIPTION OF THE DRAWINGS The invention will be further explained with reference to the drawings, in which:

FIG. I is a side view, mostly in vertical cross section, of a floating cover according to the present invention;

FIGS. 2 and 3 are vertical cross-sectional views through a pit according to the invention, together with a floating cover according to the invention with the cover in alternative positions assumedthereby during different operative conditions;

FIG. 2 shows the central portion of the pit and floating cover, and FIG. 3 shows the peripheral portions of the pit and floating cover;

FIGS, 4 and 5 are plan views of different portions of a section of the floating cover according to the invention;

FIG. 6 shows a top plan view of a part of the cover when resting on an inclined wall part of the pit;

FIG. 7 shows a top plan view of the same part of the cover as shown in FIG. 6, but floating when the pit is full;

FIG. 8 shows a top plan view of another part of the cover when resting on another inclined wall part of the pit; and

FIG. 9 shows a top plan view of the same part of the cover as shown in FIG. 7, but floating when the pit is-full.

Referring to FIGS. 1 through 5, the storage pit according to the present invention comprises a horizontal bottom 2, an inclined wall part 3, having, for example, an inclination to the horizontal of l to 15, aninclined wall part5, having, for example, an inclination to the horizontal of l to 6, an inclined wall part 5. having, for example, an inclination to the horizontal of l to and an inclined wall part 6, having, for example, an inclination to the horizontal of l to 2 5 The bottom 2 and the inclinedwall parts 3, 4, 5 and 6 comprise an underlayer of stabilized sand 7 The underlayer 7 consists of a lean sand/cement mixture, for example, with a thickness of 0.3-0.5 meter. rolled and compacted and its top surface finished smooth. The top surface of the underlayer 7 is lined with a lining 8 of, for example, three layers of fiber glass reinforced epoxy resin/coal tar. A 50/50 mixture of epoxy resin with coal tar has the advantage that it is cheaper and possesses much stronger adhesive qualities than pure epoxy resin. The lining 8 is impermeable to crude oil and many other liquids.

In order to prevent evaporation of the liquid to be stored, for example crude oil, the storage pit is provided with a floating cover 9. Attention is drawn to the fact that the pit 1 can be circular, polygonal or even square. In the embodiment shown the pit l is of polygonal shape. Furthermore, in the representative embodiment shown, the central horizontal bottom 2 has a radius of IO meters and the inclined wall parts 3, 4, S and 6 cover respectively a height of 2 meters, 2 meters, 6 meters and I6 meters. The total depth of the pit is thus 26 meters, of which the lowest 2 meters are reserved for sludge and water storage, the rest for crude oil storage.

That part of the cover 9 over the bottom 2 and the inclined wall part 3 consists of a pipe frame work 10 on legs 11. The pipes of the framework are polyurethane-filled fiber glass reinforced epoxy/coal tar pipes 12.

The framework 10 is filled in with lO-centimeters-thick slabs 13 of polyurethane foam sandwiched in between two fiber glass reinforced epoxy/coal tar sheets 14. These slabs 13 are interconnected by slabs 15 of fiber glass reinforced epoxy/coal tar sheet.

The cover 9 over the inclined wall parts 4, 5 and 6 comprises buoyant elements 16, each consisting of a polyurethane foam plate of a thickness of 10 centimeters, sandwiched .in between two fiber glass reinforced epoxy/coal tar sheets 17.

The elements I6 of the cover 9 over the inclined wall part 4 are interconnected by flexible vaportight sheet 18, for example by vaportight fiber glass cloth glued to the elements 1 6. The elements 16 adjacent to the framework 10 are connected to the framework 10 by the same sheet 18. The part of the cover 9 over the inclined wall part 4 together with the part of the cover 9 within the central framework 10 drain their rainwater through a pipe system into the pit 1. For this purpose, the slabs I3 and the elements 16 are provided with funnels 19, each provided with a protective cap 20, each of said funnels 19 being connected at its lower end through flexible conduits 21 to a conduit such as conduits 22 and 23. The conduit 22 and the conduit 23 each debouch through a flexible conduit such as conduits 24 and 25 into a pipe 26. The pipe 26 can swing in a vertical plane around a hinge 27 and is prevented from swinging too far to the right by a cable 28. The pipe 26 is provided with a mouthpiece 29 debouching into the pit 1. Thus, rainwater collected on the area of the floating cover 9 over the bottom 2 and over the inclined wall parts 3 and 4 flows through the funnels l9 and from there through conduits 21, 22 and 23 to conduit 26. From conduit 26 the collected rainwater enters the pit I. It is possible to drain this rainwater into the oil stored in the pit I since the concentrated water stream entering the pit I through pipe 26 will settle on the bottom of the pit 1 easily, where enough water storage space is available.

The part of the cover 9 over the inclined wall part 5 is substantially similar to the part of the cover 9 over the inclined wall part 4, except that the rainwater collected on the cover is discharged directly into the pit I. For that purpose inthe center of each element 16 a funnel 30 is provided. Each funnel 30 is provided with a protective cap 31 and each funnel '30 debouches at its lower side through a foil pipe 51 directly into the pit l. The elements 16 are interconnected in the same way by flexible vaportight sheet 18, for example by vaportight fiber glass cloth glued to the elements 16.

The part of the cover 9 over the inclined wall part 6 consists of the same elements 16 as in the other parts of the cover 9. However, for simplicitys sake, the drain funnels have been omitted and the rainwater collected is discharged into the pit I through tangential gaps between adjacent elements 16. The

elements 16 are interconnected by strips 32 at regular intervals.

When the illustrated pit l is completely full, the total oil surface area will be 38,000 m. In the corresponding position of the floating cover 9 there is an open oil surface of a width of about 2 cm. between the elements 16 of that part of the cover 9 which is over the inclined wall part 6. This means that the total open oil surface, when the pit is full, is about 160 m3, which is about 0.4 percent of the total surface area. Of course, it is possible that this open oil surface is considered to be too large, under certain circumstances. In that case, it is possible to close these open spaces between the elements 16 by means of vaportight cloth in the same way as done in the parts of the cover 9 present above the inclined wall parts 4 and 5; in that case, the elements 16 have to be provided with rainwater drains in the same way as the parts of the cover 9 over the inclined wall parts 4 and 5.

All necessary conduits are located in the center of the pit I, i.e., a filling line 33, a suction line 34, a rainwater drain line 35, a sludge drain line 36. For this purpose the framework of the floating cover 9 is provided with an elevated central part 37, constructed of slabs of polyurethane foam sandwiched in between glass fiber reinforced epoxy resin/coal tar sheets. Apart from the said conduits a water level indicator 3% is present in the central part of the pit I.

In the pit I there will be sufficient space available to store 1,000 m. of sludge and 3,400 m. of water, which would represent a rainfall of about l0 centimeters. The level of the sludge in the above case is indicated by the line 39 and the level of the water by the line 40. g

The central part of the empty pit should be preferably accessible and thus the central part of the cover 9 has been designed as a framework 10 on legs 11, the framework 10 being filled up with polyurethane slabs 13. Access can be obtained through a manhole 52.

The floating cover 9 is anchored at its periphery to the upper part of the wall of the pit l as indicated by the number 41 by means of a flexible strip 42, for example of fiber glass cloth. The position of the floating cover 9 when the pit l is full is indicated in full lines in FIGS. 1 and 3, whereas the position of the floating cover 9 when the pit l is empty is indicated in dotted lines.

As will be clear from the drawings, the cover 9 will have to be able to take up thereduction in area when the cover 9 moves from the position indicated in dotted lines (pit empty) to the position indicated in full lines (pit completely full). As shown in the drawings, a large part of the cover 9 is lying on the inclined wall parts when the pit 1 is empty, whereas the whole cover 9 is floating when the pit 1 is completely full. The cover 9 has to take up, when moving from the position indicated in dotted lines to the position indicated in full lines, not only a shortening in the radial direction, but also in the tangential direction.

In this respect attention is drawn to FIGS. 2, 3, 6 and 7. FIGS. 6 and 7 show respectively a top plan view of a part of the cover 9 resting on the inclined wall parts 4 and 5 and floating when the pit l is completely fulL When the cover 9 is resting on the inclined wall parts 4 and 5 tangential or substantially tangential spaces 45. are present between the elements I6. These spaces 45 are somewhat larger than necessary for taking up the shortening in radial direction when the cover 9 moves fromthe position indicated in dotted lines to the position indicated in full lines (FIGS. 1 and 3). Over the spaces 45 the vaportight sheets 18 are present.

' Since the cover 9 should also be able to take up a shortening in tangential direction, radial slits or spaces 46 are present between the elements 16 as well. These spaces 46 are so constructed that, when the cover 9 is resting on the inclined wall parts 4 and 5, they are V-shaped (see FIG. 6). Over the spaces 46 vaportight sheets 18 are present as well.

Now when the cover 9 moves from the dotted line position to the full line position as indicated respectively in FIGS. I and 3, the elements 16 displace relative to each other from the position shown in FIG. 6 to the position shown in FIG. 7. Since the sheets 18 are flexible the sheets 18 can easily take up this displacement while maintaining the vaportight seal.

The part of the cover 9 which is' empty or partly empty condition of the pit l rests on the inclined wall part 6 will now be described with reference to FIGS. 8 and 9.'FIGS. 8 and 9 show respectively a top plan of a part of the cover 9 when resting on the inclined wall part 6 and when floating when the pit 1 is completely full. When the cover 9 is resting on the inclined wall part 6 tangential or substantially tangential spaces 47 are present between the elements 16. The spaces 47 are somewhat larger than necessary for taking up the shortening in radial direction when the cover 9 moves from the position indicated in dotted lines to the position indicated in full lines (FIGS. I and 3). As explained before, the spaces 47 are open.

Since the cover 9 should also be able to take up a shortening in tangential direction, radial slots or spaces 48 are present between the elements 16 as well. These spaces 48 are so constructed that, when the cover 9 is resting on the inclined wall part 6, they are V-shaped (see FIG. 8). Over the spaces 48 vaportight sheets 18 are present. The elements I6 are interconnected by flexible joint pieces 49 and are furthermore provided with radial and rigid fixation pieces 50.

When the cover 9 moves from the dotted line position to the full line position as indicated respectively in FIGS. 1 and 3, the elements 16 displace relatively to each other from the position shown in FIG. 8 to the position shown in FIG. 9. Since the sheets 18 are flexible, they can easily take up this displacement while maintaining the vaportight seal.

We claim as our invention:

1. Apparatus for storing liquids comprising:

means defining a liquid storage pit having an inclined wall;

and expandable floating cover substantially overlying said pit, said cover comprising a central portion and an outer portion,

said central portion comprising a pipe framework operatively connected to slabs of buoyant material to form a fluidtight cover for the central portion of said storage pit,

said outer portion comprising a plurality of buoyant elements and a plurality of thin flexible fluidtight sheets movably interconnecting said buoyant elements in a fluidtight manner,

buoyant elements at the periphery of said floating cover being anchored to the upper part of the inclined wall of said pit, buoyant elements adjacent said central portion being operatively connected to said central portion by flexible fluidtight sheets,

said interconnected buoyant elements and said interconnecting flexible sheets being arranged so that when said storage pit is empty said interconnected buoyant elements rest on said inclined wall, said cover then being in an expanded condition with adjacent interconnected buoyant elements spaced apart a distance at least sufficient to allow said adjacent interconnected buoyant elements to move together in an amount such that when said storage pit is substantially full of a liquid said interconnected buoyant elements float on the surface of said liquid without overlapping adjacent buoyant elements.

2. The apparatus according to claim 1 wherein the buoyant elements consist at least partly of polyurethane foam.

3. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are lined with a sheet material.

4. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are lined with fiber glass.

5. The apparatus according to claim 1 whereinthe outer surfaces of the buoyant elements are covered with epoxy resin.

6. The apparatus according to claim 1 wherein the'outer surfaces of the buoyant elements are covered with a mixture of epoxy resin and tar.

some of said interconnected buoyant elements comprise wedge-shaped bodies which are operatively positioned so that at least two nonparallel sides of said wedge-shaped buoyant elements are substantially radially directed with respect to the center of said storage pit whereby at least some of said wedgeshaped buoyant elements are movable relative to adjacent buoyant elements in a substantially tangential direction aswell as in a substantially radial direction, said directions being defined with respect to said pit. 

1. Apparatus for storing liquids comprising: means defining a liquid storage pit having an inclined wall; and expandable floating cover substantially overlying said pit, said cover comprising a central portion and an outer portion, said central portiOn comprising a pipe framework operatively connected to slabs of buoyant material to form a fluidtight cover for the central portion of said storage pit, said outer portion comprising a plurality of buoyant elements and a plurality of thin flexible fluidtight sheets movably interconnecting said buoyant elements in a fluidtight manner, buoyant elements at the periphery of said floating cover being anchored to the upper part of the inclined wall of said pit, buoyant elements adjacent said central portion being operatively connected to said central portion by flexible fluidtight sheets, said interconnected buoyant elements and said interconnecting flexible sheets being arranged so that when said storage pit is empty said interconnected buoyant elements rest on said inclined wall, said cover then being in an expanded condition with adjacent interconnected buoyant elements spaced apart a distance at least sufficient to allow said adjacent interconnected buoyant elements to move together in an amount such that when said storage pit is substantially full of a liquid said interconnected buoyant elements float on the surface of said liquid without overlapping adjacent buoyant elements.
 2. The apparatus according to claim 1 wherein the buoyant elements consist at least partly of polyurethane foam.
 3. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are lined with a sheet material.
 4. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are lined with fiber glass.
 5. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are covered with epoxy resin.
 6. The apparatus according to claim 1 wherein the outer surfaces of the buoyant elements are covered with a mixture of epoxy resin and tar.
 7. The apparatus according to claim 1 wherein the thin flexible sheets movably interconnecting the buoyant elements comprise fluidtight glass cloth.
 8. The apparatus according to claim 7 wherein the thin flexible sheets movably interconnecting the buoyant elements are impregnated with epoxy resin.
 9. The apparatus according to claim 1 wherein the walls of the pit are lined with glass fiber reinforced epoxy resin.
 10. The apparatus according to claim 9 wherein the epoxy resin is mixed with coal tar.
 11. The apparatus according to claim 1 wherein at least some of said interconnected buoyant elements comprise wedge-shaped bodies which are operatively positioned so that at least two nonparallel sides of said wedge-shaped buoyant elements are substantially radially directed with respect to the center of said storage pit whereby at least some of said wedge-shaped buoyant elements are movable relative to adjacent buoyant elements in a substantially tangential direction as well as in a substantially radial direction, said directions being defined with respect to said pit. 